The invention relates to a light-sensitive mixture and, prepared therefrom, a recording material whereby positive or, alternatively, negative relief copies of an original can be produced.
It is known that light-sensitive materials based on naphthoquinone diazides can be used in certain process steps to obtain positive or, alternatively, negative copies.
German Offenlegungsschriften No. 2,855,723 and No. 2,529,054 describe photoresist materials based on 1,2-quinone diazides for a reversal process which contain N-acyl-N'-methylethylenediamines or hydroxyethylimidazoles as additives. A similar material containing secondary or tertiary amines is described in U.S. Pat. No. 4,196,003. European Patent Application No. 133,216 describes a reversal process where the additive in the quinone diazide layer is a hexamethylolmelamine ether which acts as a thermal crosslinking agent.
All these reversal processes are based on the fact that the light decomposition products of 1,2-quinone diazides produce an insoluble reaction product on heating. This thermal curing of the exposed 1,2-quinone diazides preferably takes place in the presence of certain basic or acid additives to the light-sensitive layer. Thermal curing is also aided by the addition of crosslinking agents. However, additions of this type in general have an adverse effect on the storage stability of the layers and on certain copying properties, for example, the light sensitivity and the image contrast after exposure to light. In addition, for many purposes the temperature required for image reversal is too high or the period of heating at a lower temperature is too long.
There have also been disclosed photoresist mixtures of the positive or negative type which, in addition to a 1,2-quinone diazide, also contain negative-working light-sensitive compounds. German Offenlegungsschrift No. 2,810,463 describes such a light-sensitive recording material whose light-sensitive components comprise a 1,2-quinone diazide and a nitrone, a requirement being that the 1,2-quinone diazide used should have a higher UV absorption in the wavelength region of 350 to 400 nm and a higher absorption in the visible region above 400 nm than the nitrone used in the mixture.
A light-sensitive material of similar composition is described in German Offenlegungsschrift No. 2,457,895; it contains a 1,2-quinone diazide in admixture with a light-curable compound. The disadvantage here is that the ratio of light-curable substance to 1,2-quinone diazide compound does not display a large tolerance and needs to be set as precisely as possible for image reversal to occur as a result of different exposure times. A further disadvantage is that the exposure times, in particular for the light-curable compounds, are relatively long. Furthermore, after positive development a prolonged postexposure of the image stencil is required to confer sufficient resistance thereon. In addition, to develop the exposed layer it is necessary that different amounts of organic solvents are added to the developer.
Other positive-working light-sensitive systems have also been used for selective image reversal. German Offenlegungsschrift No. 3,151,078 describes a corresponding process using a light-sensitive material which contains a combination of an acid-cleavable compound, for example a polyacetal, with a compound which forms an acid on irradiation, for example a trichloromethyl-s-triazine. Here too it is necessary for image reversal that, before developing, the material which has been subjected to image-wise exposure be heated at an elevated temperature for a certain period.